Render sidekiq scheduler (#2898)

config/routes.rb

@@ -1,7 +1,7 @@
-
 # frozen_string_literal: true
 
 require 'sidekiq/web'
+require 'sidekiq-scheduler/web'
 
 Rails.application.routes.draw do
   mount LetterOpenerWeb::Engine, at: 'letter_opener' if Rails.env.development?